1. Field of the Invention
The present invention relates to a video camera, and more particularly to an improved video camera for detecting a focus value engaged to an output picture which makes it possible to detect a focus value from a picture signal by being engaged to a final output picture, for thereby enabling a signal process and a automatic focus control to be carried out in greater precision.
2. Description of the Prior Art
As shown in FIG. 1, a conventional camera apparatus includes: an optical system 1 having an object lens, a zoom lens and an iris, and carrying out a photo-electric conversion in order for an object picture signal to be converted to an electric signal; an AGC (automatic gain control) circuit 2 for automatically controlling the picture signal outputted from the optical system 1; a signal process unit 3 for processing and outputting a picture signal outputted from the AGC circuit 2; an A/D (analog/digital) converter 4 for converting the gain-controlled picture signal from AGC 2 to a digital signal; a Y/C separation circuit 5 for separating the converted signal into a luminance signal and a color signal; an area varying unit 6 for receiving the digital luminance signal converted in the A/D converter 4 and carrying out a zoom area varying function; a focus value detector 7 for receiving an output signal of the area varying unit 6 and detecting a focus value Fv so as to carry out an automatic focus; a controller 8 for receiving a telephoto signal and a widephoto signal, and outputting a control signal so as to drive the optical system 1 in response to the focus value outputted from the focus value detector 7; and a driving unit 9 for driving the optical system 1 under the control of the controller 8.
The operation of the thusly constituted conventional camera apparatus will now be described.
An optical signal representing an object from the optical system 1 is converted through a CCD (charge-coupled device) to an electric picture signal, which is then gain-controlled in the AGC circuit 2 and outputted via the signal process unit 3. The gain-controlled picture signal is converted to a digital signal in the A/D converter 4 so that an area varying function is carried out through the area-varying unit 6, and together therewith a focus value Fv for the luminance signal is detected in the focus value detector 7.
The focus value Fv is applied to the controller 8 which in turn receives an externally applied telephoto/widephoto signal T/W so as to drive the optical system 1 via the driving unit 9, for thereby carrying out a zoom-in/zoom-out function and an AF (automatic focusing) operation in accordance with the focus value Fv.
In more detail, the optical system 1, the AGC circuit 2, the A/D converter 4 and the Y/C separation circuit 5 process an image signal to derive a luminance signal which is provided to the area varying unit 6. The controller 8 outputs a control signal to the area varying unit 6, but the controller 8 does not output a signal directly to the Y/C separation circuit 5.
However, the signal for carrying out the AF function in the conventional camera system is employed so as to directly apply the CCD output signal to a focus value detecting signal, so that when a zoom-in/zoom-out function is carried out against an object beyond a focus range, an accurate focusing becomes difficult.
That is, because an input data signal for generating an AF estimate value is based upon the output of the AGC circuit, when digital zooming is carried out, a focusing of the accordingly appearing picture becomes performed against an object other than the finally outputted actual picture, thereby resulting in an optical parallax against the actual object.